Fixed bed reactor is also referred to as packed bed reactor. It is filled with solid catalyst or solid reactant to realize heterogeneous reaction. The solid substance is normally in the form of particles, stacked to constitute a bed of certain height (or thickness). This bed is static and fluid flows through it for reaction. The difference between this reactor and fluidized bed reactor/moving bed reactor is that the solid particles are static. At present, liquid-solid catalytic reaction using solid catalyst and liquid reaction raw materials mainly adopts fixed bed reactor, e.g. esterification reaction and hydration reaction etc.
Advantages of fixed bed reactor: {circle around (1)} weak back-mixing, effective contact between fluid and catalyst, and relatively high selectivity in case the reaction is accompanied by side reaction in series; {circle around (2)} small mechanical loss of catalyst; {circle around (3)} simple structure; {circle around (3)} stable reaction. Disadvantages of fixed bed reactor: {circle around (1)} poor heat transfer; {circle around (2)} difficult replacement of catalyst during operation, hence not suitable for reactions that require frequent catalyst regeneration, which shall normally adopt fluidized bed reactor or moving bed reactor instead; {circle around (3)} relatively low reaction efficiency; {circle around (4)} difficult mixing of reactants involving two phases of materials, e.g. oil and water.
Jet floating bed reactor (JFBR) is a new type of intensified reactor. Its operating principle is use of high velocity mobile phase to suck other phases, generating intense stirring effect, promoting close contact among phases, and quickly completing the reaction. When used for liquid-solid catalytic reaction that adopts solid catalyst and liquid reaction raw materials, the JFBR allows full mixing of reactants and catalyst, greatly intensifies mass and heat transfer rate, improves concentration and temperature distribution inside reactor, accelerates reaction, effectively suppresses side reaction, and improves reaction selectivity.
JFBR has many unique outstanding performances: {circle around (1)} high mass transfer and heat transfer efficiency; {circle around (2)} high operation flexibility; {circle around (3)} large input power per unit volume and low energy consumption; {circle around (4)} simple reactor structure without rigid stirring, hence suitable for dangerous reactions such as oxidation and hydrogenation; {circle around (5)} good sealing performance, in particular, suitable for high pressure system; {circle around (6)} small effect of reactor scale on mixing effect and mass transfer rate, facilitating engineering amplification.
At present, industrial integrated reaction and separation system consists of reaction equipment and separation equipment combined together, and has certain defects. Examples include integrated fixed bed reaction-separation system, referred to as reaction rectifying tower, e.g. esterification reaction rectifying tower. Since relatively long reaction time is required to attain a relatively high conversion rate by means of fixed bed reactor, residence time is relatively long and equipment volume is relatively large. For other integrated reaction-separation systems, e.g. those consisting of oxidation or hydrogenation equipment and separating unit, the problem of difficult coupling between reaction and separation exists.